This invention relates to filled polyolefin compositions and processes for their preparation. More particularly, it relates to such compositions having certain coupling agents coupling the filler into the resin.
It is well known that mineral fillers can be coupled into various plastic resins by means of such agents as vinyl silanes. Also, certain chromium complexes are known in the art to be useful as coupling agents for fiberglass in resins.
Belgian Pat. No. 765,137, granted Oct. 1, 1971 and U.S. Pat. No. 3,787,326-Deyrup, granted Jan. 22, 1974, describe the use of various chromium complexes for adhering to plastics metal oxide substrates such as aluminum oxide ceramics, titanium oxide materials, and glass, with the substrate being in any desired physical form such as in the form of foils, sheets, rods and the like, or in particulate, wire or fiber forms commonly employed for reinforcing plastic objects. However, there is no recognition in the Belgian patent of the general utility of the complexes for coupling commercially used mineral silicate fillers into polyolefin resins.
Fillers are used in polyolefin resins for a variety of purposes. One frequent use is as an extender, replacing, volume for volume, relatively more expensive polyethylene or polypropylene with relatively less expensive talc or clay. Certain properties such as stiffness and heat distortion temperature may be improved by the untreated filler. However, as might be expected, such uses do frequently impair other mechanical properties of the filled composition. Coupling agents are used to diminish the loss of mechanical properties relative to the unfilled plastics. Certain commercial coupling agents such as silanes do improve mechanical properties relative to the uncoupled, filled material but do not give as good mechanical properties as might be desired, including tensile strength, flex modulus, and heat distortion characteristics.